The present invention relates to a microwave oven structure.
In general, a microwave oven has a double wall structure consisting of an interior member (a heating chamber) and an exterior member.
The construction of a conventional microwave oven is shown in FIG. 9.
As shown, a sheet member is bent into a groove-shaped three sided member 3a having side walls 5a and 7a and a bottom wall 6a, each of the side walls including connection flanges 9a, 9b and 9c in front, upper and rear ends respectively. A separately manufactured top panel 4g is placed on top of the three sided member 3a so that the left end of the former meets the upper end of the left side wall. The three sided member 3a is connected with the top panel 4g by spot welding the connection flanges 9c to the top panel 4g at the corresponding portions facing the connection flanges, thereby forming an oven body. Then, a separately manufactured front panel 11c including an opening 14 is positioned so that the edge of the opening 14 coincides with the front end edge of the oven body, and fixed to the oven body by spot welding at the connection flanges 9a. Similarly, a rear panel 13b is positioned on the rear end of the oven body so as to face the front panel 11c, and fixed to the oven body by spot welding at the connection flanges 9b. The bottom panel 12a is also fixed to the front panel 11c and to the rear panel 13b at their bottom ends by screws. Further, a waveguide 1 is placed on the top panel 4g so as to enclose waveguide openings 8 formed in the top panel 4g and fixed thereto by spot welding at connection flanges 2 of the waveguide 1.
Thus, in the conventional microwave oven structure, the constituent members are assembled with each other mainly by spot welding between the connection members.
This assembling method has various inconveniences: Defective spot welding can occur. Furthermore, the press operation for forming each member and welding operation for assembling are quite different processes and performed at different workshops, causing inefficient production procedure. In addition, since precoated steel plate cannot be welded as it is, it must be subjected to necessary treatment.
One of the solutions to the above problem in the assembly by welding is shown in FIG. 10(a), in which members A and B have respective bent ends A' and B' which are engaged with each other, the member B being further bent to be at a right angle with the member A. Another solution is shown in FIG. 10(b) in which, in the engagement between the members A and B as shown in FIG. 10(a), the member B is further bent by 180.degree. around the bent portions A' and B'. The connecting methods shown in FIGS. 10(a) and 10(b) which are employed in can manufacturing are not applicable to the connections between the waveguide 1 and the top panel 4g nor between the three-sided member 3a and the rear panel 13b, because the top panel 4g and the rear panel 13b are not provided with flanges to be engageable with the connection flanges 2 of the waveguide 1 and the connection flanges 9b of the three-sided member 3a, respectively.
Accordingly, the methods shown in FIG. 10(a) and 10(b) are not applicable for all connections. To employ these methods, it is essential that the ends of one member meet the ends of the mating member. If the methods are to be employed for connection between two members whose end edges do not meet, auxiliary mounting members (not shown) must be provided on the members, resulting in further complicated construction.